1. Field of the Invention
The present invention is related to the field of radioactivity measurement. The invention provides a method for both isotope identification and radioactivity measurement of alpha-emitting radionuclides. It is based on the calorimetric particle detection in a metallic 4π geometry using a low temperature detector.
2. Background of the Related Art
Generally, alpha spectrometry or mass spectrometry is used as a method of identifying radionuclides. Such conventional methods require many necessary chemical pretreatments which include acid digestion for solid specimens, and separation and purification of atomic species of interest. A few known concentrations of specific nuclides may be added as a tracer for an isotope dilution analysis during the pretreatment.
However, the conventional alpha spectrometry and the mass spectrometry of measuring radionuclides have the following limitations.
First, the solid-state detectors used in the conventional alpha spectrometry have a limit in their energy resolution. The identification of many radionuclides whose characteristic alpha lines are close to each other is intrinsically limited by the detector resolution. For instance, it causes difficulties in identifying 239Pu signals from 240Pu ones.
Second, the inductive coupling plasma mass spectrometry (ICP-MS), the most frequently used mass spectrometry for the purpose, often suffers from interfering overlaps of polyatomic ions of chemical matrix while it provides high mass resolution. The identification technique using ICP-MS detection requires complicated and time-consuming but necessary procedures of separations and purifications for each set of measuring isotopes. In addition, it needs adding a set of known radionuclides to the analytes in order to estimate relative concentrations of measuring radionuclides.